The present invention relates to a diffusion transfer silver halide photographic products containing a silver halide emulsion and in particular, to diffusion transfer photographic products exhibiting an enhanced sensitivity, higher maximum density, superior discrimination along with the improved white background developing temperature dependence.
Diffusion transfer process photographic light sensitive materials are known in the photographic art. A general feature of diffusion transfer photographic process is that the final image results from formation of imagewise partition of an image-providing material and diffusion transfer of the imagewise partition to an image-receiving layer.
In general, diffusion transfer images can be obtained by allowing a photosensitive element or a negative film component (having at least a photosensitive silver halide layer) to be exposes to chemical irradiation to form a developable image. Thereafter, the image is developed by being coated with an aqueous alkaline processing liquid to form an image forming partition of a soluble and diffusible image dye-providing material and then transferring the image forming partition to transmit the transferred image through diffusion to an image receiving layer overlapped onto an image receiving element or a positive film component.
In the foregoing diffusion transfer type photographic material, discrimination of the images depends on inhibition of generation or transfer of dyes in the white background areas. However, background whiteness of current diffusion transfer type photographic materials has not reached the level of commercially available color print materials. A technique of capturing a given amount of transfer dyes is supposed as a means for reducing the white background density and there have been proposed various ideas with regard to this technique. U.S. Pat. Nos. 3,930,864 and 3,958,995, for example, disclose to provide a dye-trapping layer to improve the white background. However, it was proved that, in the diffusion type silver halide photographic materials, there was a problem that providing the dye-trapping layer increased the overall thickness of the photosensitive element, leading to a decrease of the maximum density (Dmax). To avoid such a problem, JP-A No. 4-20956 (hereinafter, the term, JP-A means an unexamined, published Japanese Paten Application) discloses the use of a mordant dye polymer. Such a technique was effective but was not always sufficient.
Conventional color photographic materials including color negative films, color reversal films, color paper, color positive films and color reversal paper are processed at a constant developing temperature. On the contrary, the developing temperature range of diffusion transfer type silver halide photographic materials is so broad that sensitivity stability on variation of the developing temperature is strongly required.
Recently, requirements for photographic silver halide emulsions are more stringent and still higher levels of photographic performance are desired.
The use of tabular silver halide grains as means for enhancing the sensitivity of silver halide emulsion and in particular for enhancing the quantum sensitivity thereof are described in U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306 and 4,459,353; JP-A 58-111935, 58-111936, 58-111937, 58-113927 and 59-99433. Techniques of introducing dislocation lines are generally known as a means for enhancing sensitivity and graininess. U.S. Pat. No. 4,956,269, for example, discloses the introduction of dislocation lines into tabular silver halide grains.
The tabular grain technique described above is effective to achieve enhanced sensitivity of silver halide emulsions. However, when the dislocation lines are applied to silver halide grains having a relatively high aspect ratio (i.e., a ratio of grain diameter to grain thickness) to make the most of desired characteristics of the tabular grains, it was found that deterioration was caused in other photographic performance such as contrast, process stability or pressure resistance.
It is commonly known that application of pressure to silver halide grains causes fogging or desensitization. However, there was a problem that dislocation lines-introduced grains exhibited marked desensitization when subjected to pressure.
JP-A 59-99433, 60-35726 and 60-147727 disclose techniques for improving pressure characteristics using core/shell type grains. JP-A 63-220238 and 1-201649 disclose techniques for improving graininess, pressure characteristics and exposure temperature dependence as well as sensitivity by introducing dislocation lines into silver halide grains. Further, JP-A 6-235988 discloses a technique for enhancing pressure resistance by use of multilayer-structured, monodisperse tabular grains having a high iodide-containing intermediate shell.
Photogr. Sci. Eng. 18, 215-225 (1974) disclosed that cubic silver halide grains exhibited little desensitization in inherent sensitivity and high contrast when a sensitizing dye was allowed to be adsorbed thereon. However, specifically in the case of cubic grains, cubic grains containing 5% or less chloride, it was difficult to prepare completely cubic grains. Herein completely cubic grains refers to cubic-formed grains having overall external faces substantially formed of (100) faces. Accordingly, incompletely cubic grains refers to grains having external faces other than (100). In most cases, the face index other than (100) is (111) or (110) faces. In fact, such silver halide grains having external faces of plural face indices are different in their face proportion from each other.
JP-A 5-341417 discloses that a high proportion of (100) faces is effective in enhancing performance, but there is nothing described with respect to effects of the distribution of the face proportion per grain among all the grains.
JP-A 5-107670, 4-317050, 5-53232, 4-372943 and 4-362628 disclose techniques for introducing dislocation lines into regular crystal grains. However, it was proved that these techniques did not reach the desired levels of recent requirements for higher sensitivity, higher contrast and improved process stability and pressure resistance.
It is an object of the present invention to provide a diffusion transfer process silver halide photographic product exhibiting an enhanced sensitivity, higher maximum density, superior discrimination along with the improved white background, and developing temperature dependence.
The object of the present invention can be accomplished by the following constitution:
1. A diffusion transfer photographic product comprising a photosensitive element, an image receiving element and a container having a processing composition, wherein the photosensitive element comprises a support having thereon at least a silver halide emulsion layer containing a silver halide emulsion comprising silver halide grains and at least 50% of total grain projected area is accounted for by silver halide regular crystal grains containing 5 mol % or less chloride and 0.5 mol % or more iodide and exhibiting a proportion of a (100) face per grain of not less than 50%, a variation coefficient of the proportion of a (100) face among grains being not more than 20%;
2. The photographic product described in 1, wherein the regular crystal grains each have an internal high iodide phase having an average iodide content of not less than 7 mol % and accounting for 0.1 to 15% of the grain volume; said high iodide phase being in the region at a depth of from 7 to 27% from the (100) face, based on the distance between the center of a grain and the (100) face;
3. The photographic product described in 2, wherein the high iodide phase is at a position facing a (100) face of the grain;
4. The photographic product described in 2, wherein the high iodide phase is at a position facing a corner, an edge, a (111) face or a (110) face;
5. The photographic product described in 2, wherein the high iodide phase is in the overall region as defined in claim 1;
6. The photographic product described in 2, wherein the high iodide phase has a thickness of not more than 0.1 xcexcm;
7. The silver halide emulsion described in 1, wherein the regular crystal grains each have dislocation lines which are oriented toward the surface of the grain;
8. The photographic product described in 7, wherein the silver halide grains have at least 10 dislocation lines per grain, at least 60% of the dislocation lines being oriented toward the (100) face of the grain;
9. The photographic product described in 7, wherein the silver halide grains have at least 10 dislocation lines per grain, at least 60% of the dislocation lines of the grain being oriented toward a corner, an edge, a (111) face or a (110) face of the grain;
10. The photographic product of claim 1, wherein the regular crystal grains exhibit a variation coefficient of grain size of not more than 20%;
11. The photographic product of claim 1, wherein when the container is ruptured, the processing composition is distributed between the photosensitive element and the image-receiving element;
12. The photographic product of claim 1, wherein the processing composition exhibits a pH of not less than 12.